{"id":99328,"date":"2018-03-11T10:20:22","date_gmt":"2018-03-11T10:20:22","guid":{"rendered":"https:\/\/www.deberes.net\/tesis\/sin-categoria\/innovative-electromagnetic-designs-making-use-of-periodic-structures-and-advanced-optimization-tools\/"},"modified":"2018-03-11T10:20:22","modified_gmt":"2018-03-11T10:20:22","slug":"innovative-electromagnetic-designs-making-use-of-periodic-structures-and-advanced-optimization-tools","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/tecnologia-de-las-telecomunicaciones\/innovative-electromagnetic-designs-making-use-of-periodic-structures-and-advanced-optimization-tools\/","title":{"rendered":"Innovative electromagnetic designs making use of periodic structures and advanced optimization tools"},"content":{"rendered":"<h2>Tesis doctoral de <strong> Oscar Quevedo Teruel <\/strong><\/h2>\n<p>Abstract:  the initial purpose of this thesis was the study of microwave devices and antennas with enhanced performance by using novel forms of periodic structures (including metamaterials). In principle, the thesis was not focused on a particular type of device but it was mainly devoted to antennas and passive elements. The need of powerful optimization tools was from the beginning foreseen as one of the key aspects for the development of the thesis. Consequently, the initial work was targeted at the development of advanced optimization techniques based on evolutionary algorithms. In this sense, firstly, new versions of genetic algorithms based on hybrid techniques were explored and the no-free lunch theory was studied for a classical optimization problem: array design, as well as an introduction to the comparison of algorithms. In addition, new optimization algorithms based on ant colony concepts were developed (and applied for the first time to electromagnetic problems) with the same purpose, obtaining interesting results for a low number of iterations and individuals. Thereby, these last algorithms fit very well in problems where the cost of evaluating the goodness of a potential solution (fitness function) is computationally high, this being normally the case in electromagnetic designs.  after this initial step and upon parallel learning of concepts related to the interesting properties of periodic structures (initially electromagnetic band gap (ebg)- type and subsequently also metamaterial (mm)-type), these optimization techniques were applied to the design of microwave devices that include such structures. Particularly, two different electromagnetic designs were optimized by using an aco (ant colony optimization) algorithm. The first one was the design of a planar ebg structure for the reduction of mutual coupling between patch antennas. The antennas were printed on a multilayer substrate (with high and low permittivity layers) in order to reduce the size of the periodic elements of the ebg (with a high permittivity material), but keeping a low total effective permittivity for the patches (as antennas typically require). Moreover, mutual coupling and its reduction were also investigated for other structures, such as stacked patches and loaded pifa (planar inverted f antennas) antennas.  the second problem where the aco algorithm was applied was the design of a rectangular waveguide loaded with two lateral dielectric slabs on which srrs (split ring resonators) were printed. The loading with such metamaterials allows the propagation of new modes at frequencies below ordinary cut-off frequency of the waveguide (i.E. For miniaturization purposes) or can eliminate bands where traditionally the modes propagate. The use of the optimization tool to design the srrs with the purpose of having the most miniaturized waveguide for the new propagating mode was also successful. In addition to these previous examples, other possibilities of new structures were studied, such as ultra wide band antennas which were designed using aco algorithms with good results. Furthermore, once the waveguide with srrs was studied in depth, new designs of waveguide filters with multiple stop-bands in this technology were successfully presented. In all the investigations, the algorithm uses a full wave commercial simulator to evaluate the potential solutions.  apart from the optimization techniques, new designs of patch antennas based on or inspired by metamaterials were also proposed within this thesis with the aim of obtaining compact designs. These antennas are based on truncated structures (with a low number of repeated elements) and can radiate at frequencies lower than conventional ones. The fundamental principles of operation of these antennas, and the validation of the theoretical results with measurements on fabricated prototypes are reported in this document. Two main types of structures were studied and characterized. The first comprises circular pifas loaded with semi-rings connected to the ground plane through an electric wall. One of the main advances of this class of antennas was to provide compact devices that depending on the application may provide different radiation patterns at each band of operation. The second group involves microstrip patch antennas based on short-circuited srrs that provide two bands of operation with a higher degree of miniaturization, although in principle, with the same radiation pattern for both bands.   resumen:  el prop\u00f3sito inicial de esta tesis fue el estudio de dispositivos de microondas y antenas cuyas prestaciones fueran mejoradas mediante el uso de estructuras peri\u00f3dicas, incluidas en el t\u00e9rmino metamateriales. En principio, la tesis no se ha restringido a un tipo particular de dispositivo, aunque los estudios se centraron principalmente en antenas y elementos pasivos. Uno de los aspectos clave en el origen de la tesis, fue la necesidad de herramientas de optimizaci\u00f3n adecuadas para los problemas a estudiar. Para ello, el trabajo inicial se centr\u00f3 en desarrollar t\u00e9cnicas avanzadas de optimizaci\u00f3n basadas en algoritmos evolutivos. En este sentido, se exploraron nuevas versiones de algoritmos gen\u00e9ticos basadas en t\u00e9cnicas h\u00edbridas, siendo estudiadas para un problema de optimizaci\u00f3n cl\u00e1sico como es el dise\u00f1o de arrays, todo ello dentro de la denominada teor\u00eda del no-free lunch que permite una comparaci\u00f3n de los algoritmos. Por otro lado, con el mismo prop\u00f3sito, se desarrollaron nuevos algoritmos de optimizaci\u00f3n basados en colonias de hormigas que fueron aplicados por primera vez a problemas electromagn\u00e9ticos, obteni\u00e9ndose resultados prometedores para un n\u00famero bajo de iteraciones e individuos. De esta forma, estos algoritmos se adecuan perfectamente a problemas donde el coste de evaluar las posibles soluciones es computacionalmente elevado, siendo esto lo que habitualmente ocurre en dise\u00f1os electromagn\u00e9ticos.  despu\u00e9s de este paso inicial, se procedi\u00f3 a estudiar las propiedades de ciertas estructuras peri\u00f3dicas, a las cuales se aplicaron las t\u00e9cnicas de optimizaci\u00f3n antes mencionadas. Principalmente se optimizaron dos dise\u00f1os electromagn\u00e9ticos mediante algoritmos de colonias de hormigas. El primero fue el dise\u00f1o de ebg (electromagnetic band gap) planas para la reducci\u00f3n del acoplo mutuo entre antenas de parche. Las antenas se dispusieron sobre un sustrato multicapa (con capas de alta y baja permitividad) para reducir el tama\u00f1o de los elementos peri\u00f3dicos de la ebg (con un material de alta permitividad), pero manteniendo una baja permitividad efectiva para los parches (tal y como las antenas t\u00edpicamente requieren). Por otro lado, se investig\u00f3 tambi\u00e9n el acoplo mutuo en otras estructuras como antenas de parche apiladas y antenas pifa (planar inverted f antenna) cargadas, as\u00ed como la forma de reducirlo.  el segundo problema, donde el algoritmo de colonia de hormigas se aplic\u00f3, fue el dise\u00f1o de una gu\u00eda rectangular cargada lateralmente con dos tiras de srr (split ring resonators) impresas. Dichas tiras producen la propagaci\u00f3n de nuevos modos a frecuencias inferiores a la de corte en gu\u00edas de ondas, permitiendo por tanto, miniaturizar los dispositivos. Del mismo modo, dichas tiras pueden eliminar bandas donde tradicionalmente los modos se propagan, tal y como fue presentado tambi\u00e9n en esta tesis. Tras un previo estudio de la estructura, se plante\u00f3 el uso de herramientas de optimizaci\u00f3n para dise\u00f1ar los srr y as\u00ed obtener la mayor miniaturizaci\u00f3n posible de la gu\u00eda de ondas.  adem\u00e1s de estos ejemplos, se estudiaron otras posibilidades. Por ejemplo, se dise\u00f1aron antenas de banda ultra ancha mediante el uso de algoritmos basados en colonias de hormigas, obteniendo resultados prometedores. En todos estos ejemplos, se utiliz\u00f3 un simulador de onda completa para evaluar las posibles soluciones potenciales.  m\u00e1s all\u00e1 de las t\u00e9cnicas de optimizaci\u00f3n, tambi\u00e9n se propusieron en la presente tesis nuevos dise\u00f1os de antenas de parche inspiradas en metamateriales para la obtenci\u00f3n de dise\u00f1os compactos. Estas antenas est\u00e1n basadas en estructuras peri\u00f3dicas truncadas (con un bajo n\u00famero de elementos repetidos) y pueden radiar a frecuencias menores que las antenas convencionales. En este documento se presentaron tanto su principio fundamental de operaci\u00f3n, como resultados experimentales que sirvieron para validar los resultados obtenidos. Principalmente, se estudiaron dos estructuras. La primera fue una pifa circular cargada con anillos semicirculares conectados al plano de masa a trav\u00e9s de un muro el\u00e9ctrico. Uno de los principales avances de esta clase de antenas fue el de proporcionar dispositivos compactos que dependiendo de la aplicaci\u00f3n, pudieran radiar con diferentes diagramas en cada banda de operaci\u00f3n. Por otro lado, la segunda propuesta fue una antena de parche basada en srr cortocircuitados que proporcionan dos bandas de operaci\u00f3n con un mayor grado de miniaturizaci\u00f3n, aunque en principio, con el mismo diagrama de radiaci\u00f3n en cada banda.<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Innovative electromagnetic designs making use of periodic structures and advanced optimization tools<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Innovative electromagnetic designs making use of periodic structures and advanced optimization tools <\/li>\n<li><strong>Autor:<\/strong>\u00a0 Oscar Quevedo Teruel <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Carlos III de Madrid<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 22\/02\/2010<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3>Direcci\u00f3n y tribunal<\/h3>\n<ul>\n<li><strong>Director de la tesis<\/strong>\n<ul>\n<li>Eva Rajo Iglesias<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: magdalena Salazar palma <\/li>\n<li>stefano Maci (vocal)<\/li>\n<li>christos Christodoulou (vocal)<\/li>\n<li>zvonimir Sipus (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Oscar Quevedo Teruel Abstract: the initial purpose of this thesis was the study of microwave devices and 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